For Don Cameron, a farmer south of Fresno, a wet winter 33 years ago led to an idea about how to take advantage of the vast natural water storage system underground. He noticed that some grapevines along the San Joaquin River were flooded for months in the winter, but that those same vines produced a lush crop of grapes in the summer.

He had to wait until 2011, the last wet year before the current drought, to act on his idea. With a small government grant and help from scientists and an environmental group, Mr. Cameron diverted water to a thousand acres of the farm he manages, Terranova Ranch, deliberately flooding fields of grapes, pistachio trees and hay.

Conventional wisdom among farmers held that the roots of the crops, standing in floodwater for weeks on end, were likely to rot. “I think our neighbors thought we were crazy, to be honest with you,” Mr. Cameron recalled.

But Mr. Cameron’s fields suffered little damage. And the water soaked deep into the ground, helping to recharge the underground supply. Nowadays, Mr. Cameron is a man in demand, fielding telephone calls and interviews from around the state.

It turns out that California already has a place to store immense amounts of water, without necessarily building new dams.

Decades of overpumping have left the state’s water-bearing formations, known as aquifers, with enormous spare capacity. By some estimates, California could pump 10 times as much water into the aquifers as could be held by the new dams on the drawing board.

Such groundwater storage is already occurring in parts of the state, mainly in urban areas. It is not a perfect solution for agriculture: Water pumped into the ground and then pulled back out can pick up salts and other pollutants.

But no option confronting California farmers is perfect. Experts say this one has the potential to be far cheaper than dams. And if a new dam is built — at Temperance Flat, say - it could potentially help supply water for the aquifer-recharging projects.

The new groundwater law that the Legislature passed last year would give farmers stronger incentive to cooperate in such plans. In wet years, they might allow their fields to be flooded in the winter or early spring to recharge the groundwater, and they would then be entitled to pump a certain amount out in dry years.

Now, urgent research is underway to figure out what soils and crops can tolerate deliberate flooding. To move floodwater around in the winter, new canals and other infrastructure may be needed in some areas, one potential use of some of the $2.7 billion in public money.

If floods come this winter, Mr. Cameron will wish he were in a position to go beyond his 2011 experiment, capturing more water. But, like many farmers, he does not yet have the canals and gear in place to make that work, a big reason the farmers could be forced to watch millions of gallons of floodwater escape to the sea this winter.

Over the long term, Dr. Hanak believes, the state should not only encourage farmers to store water in the ground, but also consider creating a market to allow them to buy and sell their allotments.

Megan Konar, an engineer at the University of Illinois, Urbana-Champaign, is among the experts eager to see California lead the world toward more sustainable methods. Recent research she did with a graduate student, Landon Marston, found that 18.5 percent of the American grain supply, an essential link in the food chain, is coming from parts of the country where the aquifers are being depleted. Other research suggests that overpumping of water is even more severe in parts of India and Africa, a long-term risk to the global food supply.

As climate change forces farmers to grow crops in hotter conditions, water demand is only going to rise.

“These aquifers need to be seen as strategic national reserves that can help us weather more climate variability in the future,” Dr. Konar said. “Right now, we have pretty much the opposite situation - we’re just seeing rapid overexploitation.”